1. Field of the Invention
Embodiments of the invention relate to the field of circuit protection devices. More particularly, the present invention relates to a protection device that generates heat in an over-voltage or over-temperature situation which melts connections to a spring which then operates creating an open circuit thereby protecting a power source and related circuitry.
2. Discussion of Related Art
Over-voltage and over-temperature protection devices utilize thermal links which can melt during an abnormal situation to form an open circuit. These protection devices may be disposed between, for example, a charger and a plurality of rechargeable battery cells (e.g. Li ion batteries). When a voltage that is larger than the threshold voltage is applied to the sensing and trigger circuitry, current flows through heat generating members causing one of more thermal links to melt. Once the links are melted, an open circuit is created which prevents the over-voltage condition from damaging the battery cells. In another type of protection device, thermal cut-off functionality is used to protect the power source, e.g. battery cells. When the temperature of the cells exceeds a particular threshold level, one or more thermal links melt creating an open circuit thereby separating the charging device from the battery cells. However, the thermal coupling between the cells where the over-temperature condition exists and the thermal links may not be sufficient to ensure adequate response time, resulting in a thermal run-away condition. Accordingly, there is a need to provide a protection device configured to result in a sufficiently fast response to protect the battery cells.